Switch pkg packages, pub, and dartdoc to use package: imports.

utils/tests/pub/version_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library version_test;
 
-import '../../../pkg/unittest/lib/unittest.dart';
+import 'package:unittest/unittest.dart';
 import 'test_pub.dart';
 import '../../pub/utils.dart';
 import '../../pub/version.dart';
 
 main() {
   initConfig();
 
   final v123 = new Version.parse('1.2.3');
   final v114 = new Version.parse('1.1.4');
   final v124 = new Version.parse('1.2.4');
@@ skipping 449 matching lines @@
 
 Matcher allows(List<Version> versions) =>
     new VersionConstraintMatcher(versions, true);
 
 Matcher doesNotAllow(List<Version> versions) =>
     new VersionConstraintMatcher(versions, false);
 
 throwsIllegalArg(function) {
   expect(function, throwsA((e) => e is ArgumentError));
 }